JEE Main 2022 · 28 Jun · Shift 2 · Physics Q45

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PhysicsSingle correct+4 / -1Question 45 of 90

An EM wave propagating in $x$ -direction has a wavelength of 8 mm. The electric field vibrating $y$ -direction has maximum magnitude of 60 Vm $^{-1}$ . Choose the correct equations for electric and magnetic fields if the EM wave is propagating in vacuum :

E_y=60\sin\left[\dfrac\pi4\times10^3\left(x-3\times10^8t\right)\right]\hat j

^{-1}

B_z=2\sin\left[\dfrac\pi4\times10^3\left(x-3\times10^8t\right)\right]\hat k

E_y=60\sin\left[\dfrac\pi4\times10^3\left(x-3\times10^8t\right)\right]\hat j

^{-1}

B_z=2\times10^{-7}\sin\left[\dfrac\pi4\times10^3\left(x-3\times10^8t\right)\right]\hat k

E_y=2\times10^{-7}\sin\left[\dfrac\pi4\times10^3\left(x-3\times10^8t\right)\right]\hat j

^{-1}

B_z=60\sin\left[\dfrac\pi4\times10^3\left(x-3\times10^8t\right)\right]\hat k

E_y=2\times10^{-7}\sin\left[\dfrac\pi4\times10^4\left(x-4\times10^8t\right)\right]\hat j

^{-1}

B_z=60\sin\left[\dfrac\pi4\times10^4\left(x-4\times10^8t\right)\right]\hat k

Answer and worked solution

Official answer: B

Wave numbers. $k=\frac{2\pi}{8\times10^{-3}}=\frac\pi4\times10^3$ m $^{-1}$ , speed $3\times10^8$ m s $^{-1}$ .

Magnetic amplitude. $B_0=\frac{E_0}c=2\times10^{-7}$ T along $\hat k$ .

(B)

Topics:Properties of EM waves

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JEE Main 2022 · 28 Jun · Shift 2, Physics question 45